The data series are calculated as the average of annual mean concentrations for groundwater bodies/river stations/lake stations in Europe. Only complete series after inter/extrapolation are included (see indicator specification). The number of groundwater bodies/river stations/lake stations included per country is given in the notes below the individual substance charts.

The graphs are based on annual mean concentration trends for PM10 (top) and PM2.5 (bottom); they present the range of
concentration changes per year (in μg/m3) per station type (urban, traffic, rural and other — mostly industrial). The trends
are calculated based on the officially reported data by the EU Member States with a minimum data coverage of 75 % of valid
data per year, for at least 8 out of the 10 years period for PM10 and for at least 5 out of the 6 years period for PM2.5. In 2006,
France introduced a nation-wide system to correct PM10 measurements. French PM10 data prior to 2007 have been corrected
here using station-type dependent factors (de Leeuw and Fiala, 2009).
The diagram indicates the lowest and highest trends, the means and the lower and upper quartiles, per station type. The
lower quartile splits the lowest 25 % of the data and the upper quartile splits the highest 25 % of the data.